Use false/true mixin in migration from !3640

db/migrate/20141007100818_add_visibility_level_to_snippet.rb

 class AddVisibilityLevelToSnippet < ActiveRecord::Migration
+  include Gitlab::Database
+
   def up
     add_column :snippets, :visibility_level, :integer, :default => 0, :null => false
 
-    execute("UPDATE snippets SET visibility_level = #{Gitlab::VisibilityLevel::PRIVATE} WHERE private = true")
-    execute("UPDATE snippets SET visibility_level = #{Gitlab::VisibilityLevel::INTERNAL} WHERE private = false")
+    execute("UPDATE snippets SET visibility_level = #{Gitlab::VisibilityLevel::PRIVATE} WHERE private = #{true_value}")
+    execute("UPDATE snippets SET visibility_level = #{Gitlab::VisibilityLevel::INTERNAL} WHERE private = #{false_value}")
 
     add_index :snippets, :visibility_level
 
@@ -13,8 +15,8 @@ class AddVisibilityLevelToSnippet < ActiveRecord::Migration
   def down
     add_column :snippets, :private, :boolean, :default => false, :null => false
 
-    execute("UPDATE snippets SET private = false WHERE visibility_level = #{Gitlab::VisibilityLevel::INTERNAL}")
-    execute("UPDATE snippets SET private = true WHERE visibility_level = #{Gitlab::VisibilityLevel::PRIVATE}")
+    execute("UPDATE snippets SET private = #{false_value} WHERE visibility_level = #{Gitlab::VisibilityLevel::INTERNAL}")
+    execute("UPDATE snippets SET private = #{true_value} WHERE visibility_level = #{Gitlab::VisibilityLevel::PRIVATE}")
 
     remove_column :snippets, :visibility_level
   end